Wells of the type commonly used for fossil fuel exploration, water well drilling, geothermal energy applications and/or the like are often several kilometers deep. Typically, these wells or “boreholes” are drilled using drilling pipes (typically referred to as “drill strings”) assembled from sections (typically referred to as “pipe stands”) connected end-to-end by suitable connection joints. Pipe stands may be about 30 to 45 feet long (about 9 m to 14 m). To form a borehole, the drill string is rotated such that a drill bit attached to its “downhole” (or operative) end bites into the earth. Additional pipe stands are typically added to the “uphole” (or surface) end of the drill string as the borehole deepens.
Drilling fluid, often referred to as “drilling mud” is typically pumped through an axial bore in the drill string from the surface to the downhole end of the drill string. The drilling mud typically exits the drill string at the downhole end and returns to the surface through the space between the drill string and the borehole. The drilling mud may cool and lubricate the drill bit, power the drill bit (e.g. through hydrodynamic pressure), provide a deposit on the borehole wall to seal the formation, and remove debris from the borehole.
There is a general desire to communicate information from a downhole location at or near the end of the drill string (e.g. near the drill bit) to an uphole location (e.g. a surface location at or near the opening of the borehole). Such communication may permit monitoring of one or more sensors at the downhole location and may also permit control of the drilling operation (e.g. steering, drilling fluid pump parameters, rotational speed and/or the like) based on feedback received from such sensors. Such sensors which are referred to as measurement while drilling (MWD) sensors may sense characteristics of the drill string, the drill bit and/or the borehole. Examples of MWD sensor information may include temperature information, pressure information, incline orientation information, azimuthal orientation information, vibration information, drilling torque information and/or the like. In addition to sensor information, it may be desirable to communicate management information from the downhole location to the uphole location. By way of example, such management information may include information related to the sensor information (e.g. the amount sensor data, the type of sensor data, the transmission order of sensor data and/or the like).
One technique which has been proposed for communicating MWD information from a transmitter at a downhole location to a receiver at an uphole location involves acoustic telemetry through the drill string. These techniques comprise communicating via acoustic (or pressure) waves that travel through the drill string (e.g. through the pipe body). There is a general desire to generate, control, receive and/or otherwise create and make use of acoustic waves which may travel within and along such pipes. By way of non-limiting example, such waves can be used to communicate data along drill strings.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.